1. Field of the Invention
The present invention relates to interlayer dielectric materials and pre-applied die attach adhesives, more specifically pre-applied die attach adhesives (such as wafer and other substrate-applied die attach adhesives), methods of applying the interlayer dielectric materials onto substrates to prepare low K dielectric semiconductor chips, methods of applying the pre-applied die attach adhesives onto wafer and other substrate surfaces, and assemblies prepared therewith for connecting microelectronic circuitry.
2. Brief Description of Related Technology
Bismaleimides occupy a prominent position in the spectrum of thermosetting resins, and a number of bismaleimides are commercially available. Bismaleimides have been used for the production of moldings and adhesive joints, heat-resistant composite materials, and high temperature coatings. More recently, Henkel Loctite Corporation has commercialized a number of products based in part on certain bismaleimides for the attachment of semiconductor chips to circuit boards, which have received favorable responses from within the microelectronic packaging industry. These products are described in one or more of U.S. Pat. No. 5,789,757 (Husson), U.S. Pat. No. 6,034,194 (Dershem), U.S. Pat. No. 6,034,195 (Dershem) and U.S. Pat. No. 6,187,886 (Husson).
Low-k dielectric materials (or interlayer dielectrics, “ILD's”) play an important role in the future development of advanced integrated circuit manufacturing, enabling the application of copper interconnects in sub-0.18 micron fabrication processes. ILD's are used in integrated circuit manufacturing to insulate copper interconnects from their surroundings, ensuring less cross talk between interconnections. Cross talk is a common problem in integrated circuit manufacturing, as it causes malfunctions in the circuit. Cross talk becomes even more pronounced as the integrated circuit continues to be designed smaller and smaller. And ILD's are an important aspect of this design trend to maximize the efficiency of ever more compact integrated circuits.
Many in the industry even view ILD's as a potential successor to silicon oxide insulators. Little progress has been reported to date, however, at reducing the internal package stresses that lead to the ILD cracking failures.
It would be desirable therefore to provide ILD's with superior dielectric properties to minimize cross talk. In addition, it would be desirable to provide electronic packages assembled with such ILD's and methods of manufacturing such electronic packages that provide enhanced physical properties.
It would also be desirable to provide die attach adhesive materials in a pre-applied form, such as a wafer-applied or substrate-applied version thereof. Such a version would eliminate many of the storage, dispensing, handling and processing issues that exist when dispensing in a flowable form reactive adhesives, including die attach adhesive materials.
In addition, in more extreme environments, such as those elevated temperature conditions to which a semiconductor device may be exposed during the solder reflow cycle where a lead free solder is used to establish electrical interconnection, it would be desirable to use in the pre-applied die attach adhesive material a material which is even more robust than the maleimides to which reference is made above.
Pre-applied adhesives themselves are not a new commercial product. For instance, Henkel Loctite has a substantial business in pre-applied threadlocker adhesives, which involve (meth)acrylate chemistry, for use in connection with nut and bolt assemblies, curable by either a photocure mechanism, a heat cure mechanism, or combinations thereof, with an optional secondary anaerobic cure mechanism. See also International Patent Application No. PCT/US00/07494; and U.S. Pat. Nos. 2,928,446, 4,325,985, 4,632,944 and 5,300,608.
However, to date there has not been an article of manufacture placed in commerce, such as a semiconductor chip or a semiconductor wafer, with a die attach adhesive material pre-applied thereon for application without the intermediate process steps attendant with a flowable die attach adhesive material, particularly where the reactive component of the adhesive material is based in whole or in part on a bismaleimide or for more extreme environments where the reactive component of the die attach adhesive material is based in whole or in part on a benzoxazine.